THERMAL FRONT IN THE GERLACHE STRAIT REVEALS TWO DISTINCT PHYTOPLANKTON PATTERNS IN NEARSHORE AREAS (64° - 65° S, ANTARCTICA)

MASCIONI, MARTINA; ALMANDOZ, GASTÓN O.; CUSICK, ALLISON; PAN, B. JACK; FERRARIO, MARTHA E.; VERNET, MARIA

Congreso; 12th International Phycological Congress; 2021

International Phycological Society

The Gerlache Strait is a highly productive coastal area, a breeding and feeding location for penguin, seal, and whale populations, located on the western coast of the Antarctic Peninsula (WAP). Several previous studies recorded a thermal front in the Gerlache Strait around 64.5° S during summer, separating warmer waters to the north and colder waters to the south, but little is known on its effect on phytoplankton distribution. The setting of a citizen science project ? FjordPhyto ? in collaboration with the International Association of Antarctica Tour Operators vessels (IAATO) allowed us to analyze by light and electron microscopy phytoplankton biomass and composition in six nearshore areas connected to the Gerlache Strait between 64° and 65°S, from November to February 2016?2018. The thermal front in the Gerlache Strait divides these areas in two zones: 1) northern areas, Cierva Cove and Wilhelmina Bay; and 2) southern areas, Cuverville and Danco Islands, Neko Harbor, and Paradise Bay. In both years we were able to identify two different patterns of biomass and phytoplankton composition. Biomass in the northern areas was considerably lower than in the southern ones, mainly during December and January. In the warmer northern areas, the abundance was dominated by cryptophytes and small flagellates. In the colder southern areas, the abundance was dominated mainly by small flagellates and diatoms, with important contributions of prasinophytes during January. This study reveals two different phytoplankton composition patterns north and south of the thermal front in the Gerlache Strait during two consecutive austral summers.